[Association of Polymorphic Genome Variants in the 2q32.1 Locus with the Development of Vasovagal Syncope]

The vasovagal syncope (VVS) is the most common form of syncope. The mechanisms of VVS development are not entirely clear. It is known that there is a genetic predisposition to this disease, but the data on the roles of individual genes are quite contradictory. Recently, a genome-wide association study identified a locus at chromosome 2q32.1 associated with a united group of diseases, that is, syncope and collapse; among the single nucleotide polymorphisms (SNPs) of this locus, the most significant association was observed for rs12465214. In a homogeneous sample of patients diagnosed with VVS, we analyzed the association of rs12465214, rs12621296, rs17582219 and rs1344706 located on chromosome 2q32.1 with this form of syncope. In the enrolled set, only rs12621296 was associated with VVS by itself, whereas associations of other SNPs were observed only in biallelic combinations. An epistatic interaction between the components of the combination rs12621296*A + rs17582219*A was revealed. The possible involvement of individual genes on the 2q32.1 locus in the genetic architecture of the VVS is discussed.

[Risk of Multiple Sclerosis: Analysis of Interactions Between Variants of Nuclear and Mitochondrial Genomes]

There is increasing evidence that the interaction of the mitochondrial and nuclear genomes substantially affects the risk of neurodegenerative diseases. The role of mitonuclear interactions in the development of multiple sclerosis, a severe chronic neurodegenerative disease of a polygenic nature, is poorly understood. In this work, we analyzed the association of multiple sclerosis with two-component mitonuclear combinations that include each of seven polymorphic variants of the nuclear genome localized in the region of the UCP2, and KIF1B genes and in the PVT1 locus (MYC, PVT1, and MIR1208 genes) and each often polymorphisms of the mitochondrial genome, as well as individual genetic variants that make up these combinations. Association of the individual components of these combinations with multiple sclerosis was also evaluated. 507 patients with multiple sclerosis and 321 healthy individuals were enrolled in the study, all participants were ethnic Russians. Two mitonuclear combinations associated with multiple sclerosis were identified: the UCP2 (rs660339)*A + MT-ATP6 (rs193303045)*G combination was characterized by p-value = 0.015 and OR= 1.39 [95% CI 1.05-1.87], and the PVT1 (rs2114358)*G + MT-ND1 (rs1599988)*С combination - by p-value = 0.012 and OR = 1.77 [95% CI 1.10-2.84]. Only one of the individual components of these combinations, allele rs660339*A of the nuclear gene UCP2 encoding uncoupling protein 2 of the mitochondrial anion carrier family, was independently associated with multiple sclerosis (p = 0.028; OR = 1.36 [95% CI 1.01-1.84]). This study expands the current understanding of the role of mitonuclear interactions and variance of nuclear genes, whose products function in mitochondria, and in risk of MS.

[The role of mitochondria in pathological mechanisms of innate immunity in multiple]

The review discusses the role of mitochondria in multiple sclerosis (MS). Previously, damage to the mitochondria was regarded as a manifestation of secondary damage to axons and neurons, i.e. as a marker of neurodenegation. Recently, the role of mitochondria in the early stages of MS development, when they could participate in the activation of innate immunity and trigger activation of autoimmune responses of acquired immunity, has been increasingly discussed. The role of polymorphism mitochondrial DNA changes in MS is discussed.

The combined effect of nuclear and mitochondrial genomes on the risk of developing multiple sclerosis

Multiple sclerosis (MS) is a severe chronic CNS disease characterized by autoimmune inflammation, demyelination, and neurodegeneration. The interaction of mitochondrial and nuclear genomes is shown to be important in the formation of a predisposition to many diseases.

Objective: to analyze the association of MS with the carriage of biallelic combinations, including as components the polymorphisms of three genes of mitochondrial DNA (mtDNA) and those of 16 nuclear genes, the products of which are involved in the functioning of the immune system and may participate in the development of autoimmune inflammation in MS; and, if these combinations are identified, to determine the nature of an interaction between their components.

Patients and methods. The investigation enrolled 540 MS patients and 406 control group individuals; all were Russians. The mitochondrial genome was genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis. APSampler software was used for multilocus association analysis. 

Results and discussion. The investigators identified five biallelic combinations that were associated with MS (p=0.0036–0.022) and possessed protective properties (odds ratio (OR) 0.67–0.75). The mitochondrial component of the identified combinations was the polymorphisms m.4580 (rs28357975), m.13368 (rs3899498), and m.13708 (rs28359178) mtDNA; the nuclear component was CXCR5 (rs523604), TNFRSF1A (rs1800693), and CD86 (rs2255214) gene polymorphisms. The interaction between the components of the identified combinations was additive.

Conclusion. The data obtained in the Russian population suggest that the combined contribution of the mitochondrial and nuclear genomes may affect the risk of developing MS.

[Variability of the Mitochondrial Genome and Development of the Primary Progressing form of Multiple Sclerosis]

Recently, it has been shown that dysfunction of mitochondria is an important component of the molecular mechanisms of the development of many neurodegenerative diseases. These include multiple sclerosis, a chronic autoimmune and neurodegenerative disease of the central nervous system, which is characterized by clinical heterogeneity. The role of genetic variability of mitochondrial DNA in the development of various clinical forms of multiple sclerosis is poorly understood. The aim of present study was to analyze the association often mitochondrial DNA single nucleotide polymorphisms and the nine most common European mitochondrial haplogroups (H, J, K, U, T, I, V, W and X) with a severe and relatively rare multiple sclerosis disease form-primary progressive multiple sclerosis. 110 patients with primary progressive multiple sclerosis and 406 healthy controls were enrolled in the study, all ethnic Russians. For the first time association of the m.12308*G (rs2853498) variant (P = 0.024) and haplogroup U (P = 0.0004, passes the adjustment for multiple comparisons: Pcorr = 0.0076) with primary progressive multiple sclerosis was shown. Comparison of these data with the results of our previous study [1], that was focused on the role of mitochondrial genome variability in susceptibility to the most common form of multiple sclerosis, relapsing-remitting multiple sclerosis, leads to the conclusion that two different mitochondrial haplogroups, U and J, are involved in the development of two different clinical forms of multiple sclerosis. The results may contribute to the identification of new targets for the treatment of primary progressive multiple sclerosis, for which there is no effective pathogenetic treatment at the moment.

Mitochondrial genome and risk of multiple sclerosis

Mitochondrial DNA (mtDNA) polymorphism makes a certain contribution to the formation of a genetic risk of multiple sclerosis (MS).

Objective: to analyze the frequency of mtDNA variants in patients with MS and control individuals in the Russian population. A similar study was conducted for the first time.

Patients and methods. The polymorphism of mtDNA was studied in the Russian population: in 283 unrelated patients with relapsing-remitting MS and in 290 unrelated healthy controls matched for gender and age.

Results and discussion. The frequency of haplogroup J in the patients with MS was twice higher than that in the control group (p=0.0055) (odds ratio (OR) 2.00; 95% confidence interval (CI). 1.21–3.41). This association was mostly observed in women (p=0.0083) (OR 2.20; 95% CI, 1.19–4.03). There was also a significant association of the A allele of MT-ND5 (m. 13708G>A) with MS (p=0.03) (OR 1.89; 95% CI 1.11–3.32). Sex stratification showed that the association with MS was significant only in women (p=0.009; OR, 2.52; 95% CI, 1.29–5.14). Further investigations will aim to analyze mtDNA variability (at the level of individual polymorphisms, haplogroups, and whole genome) in patients with relapsing-remitting MS and in those with primary progressive MS versus healthy individuals and patients with relapsing-remitting MS according to disease severity.

Conclusion. The data obtained in the Russian population suggest that mtDNA variations are involved in MS risk, to a greater extent in women. 

Variants of Mitochondrial Genome and Risk of Multiple Sclerosis Development in Russians

For the first time in the history of ethnic Russians, an association analysis the development of multiple sclerosis (MS) was performed for the mitochondrial haplogroups H, J, K, and U, as well as for the individual mitochondrial DNA (mtDNA) polymorphisms discriminating these haplogroups (m.1719G A, m. 7028C T, m.9055G A, m.10398A G, m.12308A G). A total of 283 unrelated patients with the relapsing-remitting form of MS and 290 healthy controls were enrolled in the study. Association of haplogroup J with MS was observed (P = 0.0055, OR = 2.00 [95% CI 1.21-3.41]). After gender stratification, the association remained significant in women (P = 0.0083, OR = 2.20 [95% CI 1.19-4.03]). A multilocus analysis of the association between combinations of mtDNA haplogroups with variants of 38 nuclear immune-related genes and MS risk was carried out. MS-associated biallelic combinations of haplogroup J with the alleles CCL5 rs2107538*A, PVT1 rs2114358*G, TNFSF14 rs1077667*C, and IL4 rs2243250*C, which were not associated with MS individually, were identified. For the combination of haplogroup J and the CCL5*A allele (P = 0.00043, OR = 5.47 [95% CI 1.85-16.15]), a epistatic (synergistic) interaction between the components was established using two statistical criteria: the PFLINT value in the Fisher-like interaction numeric test and the synergy factor, SF (PFLINT = 0.025, SF = 4.32 [95% CI 1.20-15.60]). The combination of haplogroup J and the PVT1*G allele is characterized by PFLINT = 0.084; SF = 3.05 [95% CI 1.00-9.31] and can also be epistatic. Thus, interaction between nuclear and mitochondrial genome components in the risk of developing MS was demonstrated for the first time.

Variants of Mitochondrial Genome and Risk of Multiple Sclerosis Development in Russians

For the first time in the history of ethnic Russians, an association analysis the development of multiple sclerosis (MS) was performed for the mitochondrial haplogroups H, J, K, and U, as well as for the individual mitochondrial DNA (mtDNA) polymorphisms discriminating these haplogroups (m.1719G > A, m. 7028C > T, m.9055G > A, m.10398A > G, m.12308A > G). A total of 283 unrelated patients with the relapsing-remitting form of MS and 290 healthy controls were enrolled in the study. Association of haplogroup J with MS was observed (P = 0.0055, OR = 2.00 [95% CI 1.21-3.41]). After gender stratification, the association remained significant in women (P = 0.0083, OR = 2.20 [95% CI 1.19-4.03]). A multilocus analysis of the association between combinations of mtDNA haplogroups with variants of 38 nuclear immune-related genes and MS risk was carried out. MS-associated biallelic combinations of haplogroup J with the alleles CCL5 rs2107538*A, PVT1 rs2114358*G, TNFSF14 rs1077667*C, and IL4 rs2243250*C, which were not associated with MS individually, were identified. For the combination of haplogroup J and the CCL5*A allele (P = 0.00043, OR = 5.47 [95% CI 1.85-16.15]), a epistatic (synergistic) interaction between the components was established using two statistical criteria: the PFLINT value in the Fisher-like interaction numeric test and the synergy factor, SF (PFLINT = 0.025, SF = 4.32 [95% CI 1.20-15.60]). The combination of haplogroup J and the PVT1*G allele is characterized by PFLINT = 0.084; SF = 3.05 [95% CI 1.00-9.31] and can also be epistatic. Thus, interaction between nuclear and mitochondrial genome components in the risk of developing MS was demonstrated for the first time.

Involvement of Mitochondria in Neurodegeneration in Multiple Sclerosis

Functional disruption and neuronal loss followed by progressive dysfunction of the nervous system underlies the pathogenesis of numerous disorders defined as "neurodegenerative diseases". Multiple sclerosis, a chronic inflammatory demyelinating disease of the central nervous system resulting in serious neurological dysfunctions and disability, is one of the most common neurodegenerative diseases. Recent studies suggest that disturbances in mitochondrial functioning are key factors leading to neurodegeneration. In this review, we consider data on mitochondrial dysfunctions in multiple sclerosis, which were obtained both with patients and with animal models. The contemporary data indicate that the axonal degeneration in multiple sclerosis largely results from the activation of Ca2+-dependent proteases and from misbalance of ion homeostasis caused by energy deficiency. The genetic studies analyzing association of mitochondrial DNA polymorphic variants in multiple sclerosis suggest the participation of mitochondrial genome variability in the development of this disease, although questions of the involvement of individual genomic variants are far from being resolved.